Cory Booker, as mayor of Newark, projects leadership in a city that desperately needs it. Actually, two cities need Newark to have a strong mayor: Newark and New York.

Since taking office in July 2006, Mr. Booker has taken decisive steps to rebuild Newark. He started by significantly reducing violent crime by about 30 percent. Newark is a safer place to live and work, and that goes a long way toward reversing the reputation of a big city in decline. He regained control of the city’s school system and improved public housing.

Just as important, he has led the city by example. He trimmed his own salary and denied his staff raises, consistent with the fiscal restraint he has tried to impose on Newark. More than almost any big-city mayor, Mr. Booker has plugged himself into social media, making himself accessible and responsive to constituents. Yes, his efforts to eat for a week on a SNAP budget of $30 and dig constituents out after a snowstorm are symbolic. But they are symbolic of a mayor and an administration that follows up words with deeds.